Histological heterogeneity and distributional difference of gastric carcinosarcoma: report of 4 cases and literature review.

Carcinosarcoma is a rare malignant neoplasm, consisting of both epithelial and mesenchymal component. Primary gastric carcinosarcoma is rare and poorly understood. We reported clinicopathologic features of 4 cases and analysis of 76 cases published in the literature. Clinical symptoms were nonspecific with epigastric pain, weight loss, and melena, as the most common complaints. The prognosis of patients was dismal with high mortality. The tumor commonly occurred in the upper stomach in Chinese patients, whereas, it was more prevalent at the lower stomach in Japanese and other populations. The two malignant components of this rare cancer showed considerable histological heterogeneity with a wide range of differentiation. We propose that carcinosarcomas be divided in two main subtypes: conventional carcinosarcoma and carcinosarcoma, not-otherwise-specified (NOS). Such distinction may provide useful information for targeted treatment of various sarcomatous components of this tumor. Immunohistochemistry should be routinely applied in the diagnosis of this rare tumor.